Battery Power Limit Control Using Voltage Deviation Feedback
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Solution Overview
Problem
Conventional battery control devices fail to accurately calculate available input/output power due to neglecting the ion concentration gradient in the diffusion layer, leading to calculation errors and battery voltage deviations during high-current charging or discharging.
Innovation Solution
A battery control system that includes a correction factor calculation unit to determine a correction factor based on the deviation between measured and modeled battery states, and a power limit value calculation unit that employs this correction to accurately calculate available input/output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a voltage equivalent circuit model is used to calculate battery internal resistance and available input/output power, then the calculation process is simplified and can be executed in real-time, but calculation errors occur when the battery is charged and discharged in ranges that cannot be reproduced by the model, leading to inaccurate available power calculation and battery voltage deviation from limit values
Solution Approach 1:
The patent implements a feedback mechanism where the calculated battery voltage from the equivalent circuit model is continuously compared with the actual measured battery voltage. When a deviation is detected, the system automatically corrects the internal resistance value to align the calculated voltage with the measured voltage, ensuring accuracy while maintaining real-time calculation capability.
Solution Approach 2:
The patent dynamically adjusts the internal resistance parameter based on the deviation between calculated and measured voltages. By changing the internal resistance value in response to operating conditions and detected deviations, the system maintains accurate available power calculation across different charge/discharge ranges without sacrificing real-time performance.
2Device complexity
If the upper limit current value is set without considering the lithium ion concentration gradient in the diffusion layer, then the control system is simpler to implement, but the battery voltage changes abruptly in the high-current range causing battery degradation
Solution Approach 1:
The system uses feedback from actual battery voltage measurements to detect abrupt changes caused by lithium ion concentration gradients. When such changes are detected, the control system automatically adjusts the current limit to prevent battery degradation, maintaining reliability without requiring complex predictive models of ion concentration.
3Measurement precision
If correction based on deviation between measured and calculated battery states is applied to calculate available power, then the available input/output power calculation accuracy is improved, but the calculation process becomes more complex
Solution Approach 1:
The patent corrects the internal resistance parameter by comparing calculated and measured voltages and adjusting the parameter accordingly. This single parameter correction approach improves available power calculation accuracy while adding minimal complexity to the calculation process, as it builds upon the existing equivalent circuit model framework.
Data Source
AI summary
An object is to determine available input/output power of a battery with high accuracy. A battery control device includes: a correction factor calculation unit that determines a correction factor based on a deviation between a state of a secondary battery determined from a measured value related to the secondary battery and a state of the secondary battery calculated using a model related to the secondary battery; and a power limit value calculation unit that employs correction based on the correction factor to calculate a value related to available input/output power of the secondary battery. A ratio between voltage change in internal resistance based on an actual measured voltage obtained by measuring voltage of the secondary battery, and a voltage change in internal resistance based on a model voltage determined using a voltage equivalent circuit model of the secondary battery can be determined as the correction factor.